1. Field of the Invention
The invention generally relates to instruments for the generation and use of ultrasonic energy and more particularly relates to such apparatus in which energetic ultrasonic waves are generated and efficiently coupled through a small area of entry into an object to be excited by such waves.
2. Description of the Prior Art
In the past, instruments have been widely devised for the generation of ultrasonic waves of high mechanical energy for industrial applications such as for cleaning, welding, and the like. While many of these devices operate with some success at moderate or high power levels, they are not readily useful for ultrasonic testing of precision instruments and especially for testing of small parts of such instruments, such as ball bearings. In testing applications, it is often desired that the ultrasonic energy be injected into a small surface of the small object to be tested as a flowing wave. It is also desirable that the carrier frequency of the ultrasonic wave be varied over a considerable range to enable study of resonance effects in the objects being tested. Many prior art ultrasonic drivers themselves exhibit interior multiple reflections or resonance effects with the consequent generation of nulls which shift location within the driver device as carrier frequency or other factors are changed. Evidently, the presence of such undesirable effects within the driver itself is extremely troublesome in that they may entirely mask the resonance effect it is desired to detect and to measure.